This invention relates to lead-acid storage batteries in which the individual cell groups are electrically series connected by intercell connectors formed through apertures in intercell partitions of the case housing the battery. More specifically, this invention relates to a method of forming a strong, low impedance intercell connector.
Through-the-partition intercell connections are used in batteries as a means for reducing IR losses within the battery, reducing the weight and cost of materials (i.e., lead) and improving the esthetics of the battery. A number of methods for making such connectors have been proposed over the years, but only a few of them have ever become a commercial reality. In this regard, Doyle et al U.S. Pat. No. 2,942,055, Miller U.S. Pat. No. 3,336,164, Sabatino et al U.S. Pat. No. 3,313,658, Matter U.S. Pat. No. 4,046,062 and variations thereof have all received some degree of commercial use. Doyle and Miller both involve mechanically upsetting a connector member extending through the aperture in the partition. Doyle upsets a discrete connector pin into sealing engagement with the aperture and subsequently fuses it to the plate strap lugs. In Miller, the connector is a male projection integral with one of the plate strap lugs. Miller's projection extends through the aperture, mates with a female plate strap lug on the cell group in the next adjacent cell and is mechanically upset into locking-sealing engagement with the female lug and the partition wall. Sabatino et al form their connector by resistance welding lug-integral projections together within the partition aperture. During welding, the lug faces move together into sealing engagement with the partition surrounding the aperture, and the softened projections deform to fill the aperture. Matter presses substantially flat-faced lugs tightly against the partition walls and thereafter, by means of opposing extruder-electrodes, extrudes portions of the lugs into contact with each other within the aperture. When the extrusions contact one another inside the aperture, the flowing current causes melting of the extrusions and softening of the surrounding material, and the pressure applied by the extruder-electrodes causes filling of the aperture with the extrudate.
Adams U.S. Pat. No. 3,589,948 confines flat plate strap lugs within molds located on opposite sides of the intercell aperture and then melts (e.g., by gas torch) down the tops of the lugs such that the melt flows together into the aperture. The application of heat such as to melt the tops of the lugs and cause them to flow together as suggested by Adams tends to overheat and distort thermoplastic (i.e., polypropylene) intercell partitions. This is especially true when heating is effected by gas torching the lug tops under conditions where the flame can directly contact the intercell partition.
It is an object of the present invention to provide an arc welding process for the precise manufacture of strong, low impedance intercell connections within the narrow confines of a lead-acid storage battery cell compartment without deleteriously overheating the intercell partition. This and other objects and advantages of the present invention will become more readily apparent from the detailed description thereof which follows.